We will be taking the train to the Jungfrauhoch in mid September and do not know the area at all with regards to hiking. I am an experienced worldwide hiker. I will be travelling with 2 fit inexperienced hikers, who live and ski in Switzerland so know the terrain/conditions but have no hiking experience, and do not know this area. Firstly, is it possible to hike down from Jungfrauhoch on marked paths with no specialist equipment? If not what are the options for us to hike back to Wengen from any intermediate point? Thank you.

No, you cannot hike down the Jungfrau, it's covered with a permanent snow field atop a permanent glacier.

Your best bet with inexperienced hikers is to take the train from Jungfraujoch back down to Kleine Scheidegg, then walk up to Männlichen. About 500 feet of vertical ascent over about 3 miles. Lovely panorama of Eiger, Mönch, and Jungfrau. From Männlichen take the gondola down to Wengen.

You can also walk down from Kleine Scheidegg to Wengen (opposite direction than up to Männlichen) but it is steep in places and inexperienced hikers will not be happy.

Actually we were just there at the end of June 2012 - If you'd like a little longer hike (downhill) you can get off the Jungfraubahn at Eigergletscher station (just above Kleine Scheidegg) and walk down to Kleine Scheidegg (lunch?), then on to Mannlichen. Maybe they've repaired it by now, but when we hiked that "500 feet of vertical ascent over 3 miles" between Kleine Scheidegg and Mannlichen, about the first 0.5 miles of that "easy route" was closed due to a rockslide - the detour was quite arduous, narrow and two-way traffic on a very popular route that we felt made it more dangerous and stressful than what we expected. A month or more hence I assume that the regular path is open again, but I don't know how to check - maybe the moderators know somebody to call. In any case, the views are wonderful and ever-changing the entire walk. I would highly recommend it.